Microbiology and Parasitology for nutrition students undertaking diploma or degrees in Nutrition and dietetic.

1. MICROBIOLOGY
DIPLOMA IN NUTRITION HEALTH
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2. ON FACEBOOK:’’MEDICAL MICROBIOLOGY’’,LIKE THE PAGE AND LETS
INTERACT
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3. As we wait
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4. THE FOOD WE LOVE
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5. WE HAVE THE OPTIONS!
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6. MEAT CAN GO BAD……
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7. WOULD YOU CRY!
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8. CONSULT A NUTRIONALIST!
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9. Food microbiology
• Food microbiology is the study of the
microorganisms that inhabit, create, or
contaminate food and the study of
microorganisms causing food spoilage.
• What is the importance of food microbiology?
• To study microorganism causing food
spoilage,fermentation,and yeast production
essention in food production
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10. • What is Microbiology?
• Microbiology is the study of microorganisms, that
exist as single cells or cell clusters; it also includes
viruses, which are microscopic but not cellular.
• Parasite
• Living organism that live in or on a host that
provide physical protection and
nourishment.term usually applied to protozoans
and helminths
• What is Parasitology?
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11. Roles of microorganisms found in
food
 Spoilage, fermentation, food production.
 Microorganisms are used in brewing,
winemaking, baking, pickling and other food
-making processes.
 They are also used to control the
fermentation process in the production of
cultured dairy products such as yogurt and
cheese. The cultures also provide flavour
and aroma, and inhibit undesirable
organisms.
 Do you think bacteria can be consumed as
prophylactic measures?
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12. Primary sources of microorganisms
1.
2.
3.
4.
5.
6.
7.
8.
Soil and water
Plant and plant products
Food utensils
Git of animals and humans
Food handlers
Animal hides
Air and dust
Animal feeds
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13. Primary source of food poisoning
bacteria
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14. Synopsis of common food borne
bacteria
• A synopsis is provided to give you a glimpse
of what we are going to encounter in the
course of our study.
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15. WALTER WAKHUNGU WASWA
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16. Synopses of Genera of Moulds
common to food
• assignment1
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17. Synopsis of Genera of Yeasts
common to foods
• Assignment2
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18. Synopsis of mould
• Molds are filamentous fungi that grow in the form of a tangled
mass that spreads rapidly and may cover several inches of area
in 2 to 3 days.
• The total of the mass or any large portion of it is referred to as
mycelium. Mycelium is composed of branches or filaments
referred to as hyphae.
• Those of greatest importance in foods multiply by ascospores,
zygospores, or conidia.
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19. cont
•
•
•
•
•
•
•
•
•
Aspergillus
Aureobasidium (Pullularid).
Botrytis.
Byssochlamys.
Cladosporium
Colletotrichum.
Fusarium.
Penicillium
Rhizopus.
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20. SYNOPSIS OF COMMON GENERA OF
FOODBORNE YEASTS
Yeasts may be viewed as being unicellular
fungi in contrast to the molds, which are
multicellular;
Some yeast produce mycelia to varying
degrees.
Yeasts can be differentiated from bacteria
by
their larger cell size and their oval, elongate,
elliptical,or spherical cell shapes.
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21. Genus:
Brettanomyces
Candida
Cryptococcus
Rhodotorula
Trichosporon
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22. The Causes of Food Spoilage
• INTRINSIC PARAMETERS
• This are parameters of plant and animal tissues
that are an inherent part of the tissues .
• These parameters are as follows:
• pH
• Moisture content
• Oxidation-reduction potential (Eh)
• Nutrient content
• Antimicrobial constituents
• Biological structures
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23. Conditions for Spoilage
•Water
•pH
•Physical structure
•Oxygen
•temperature
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24. Microorganism Growth in Foods
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25. Composition and pH
• putrefaction
– proteolysis and anaerobic breakdown of proteins,
yielding foul-smelling amine compounds
• pH impacts make up of microbial community and
therefore types of chemical reactions that occur
when microbes grow in food
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26. Water availability
• in general, lower water activity inhibits microbial
growth
• water activity lowered by:
– drying
– addition of salt or sugar
• osmophilic microorganisms
– prefer high osmotic pressure
• xerophilic microorganisms
– prefer low water activity
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27. Physical structure
• grinding and mixing increase surface area
and distribute microbes
– promotes microbial growth
• outer skin of vegetables and fruits slows
microbial growth
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28. Antimicrobial substances
• coumarins – fruits and vegetables
• lysozyme – cow’s milk and eggs
• aldehydic and phenolic compounds – herbs
and spices
• allicin – garlic
• polyphenols – green and black teas
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29. Extrinsic parameters
• These are those properties of storage environment
that affect both the foods and their
microorganisms.
1.temperature
I.
lower temperatures retard microbial growth
2.relative humidity
I.
higher levels promote microbial growth
3.atmosphere
I. oxygen promotes growth
II. modified atmosphere packaging (MAP)
III. use of shrink wrap and vacuum technologies to
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package food in controlled atmospheres
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30. Incidence and types of
microorganisms in food
Fresh meat and poultry
• Primary sources and routes of microorganisms
• 1.stick knife
• 2.animal hide
• 3.git
• 4.hands of handlers
• 5.containers
• 6.handling and storage environment
• 7.Lymph nodes
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31. Extended ground meat
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32. • EXTENDED by addition of soy flour and frozen
• Ie chicken soy blend
• However bacteria grow faster in meat soy
blend meat than non extended
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33. • Ground meat or comminuted meat
• Higher level of contamination.
– Higher surface area
– Meat grinders, cutting knives, storage utensils
– One heavily contaminated meat portion ie lymph
node
• Bacteria
– Bacilli and
– Clostridium botulinum,perfringens,JEJUNII
– E.coli
– S.aureus
– Klebsella pneumoniae,Enterobacter cloacae
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34. • Mechanically deboned meat
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35. •
•
•
•
By machines
Less contact by man
Which bacterial group is minimized?
Coliforms
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36. Hot boned meat
• Processing meat 1-2 hrs after slaughter while
carcass is still hot(pre rigor)
• COLD BONED MEAT?
• Mesophiles elevated
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37. • Organ and variety meat
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38. • Liver kidney hearts tongues
• Higher ph and glycogen levels
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39. • Vaccuum packaged meat
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40. • Anaerobic bacteria will survive
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41. •
•
•
•
Storage of various meat products
Bacon
Sausage
bologna
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42. • poultry
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43. • Sea food
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44. • vegetables
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45. • Delicatessen
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46. • Frozen meat pie
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47. • Dehydrated foods
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48. Microbial Growth and Food Spoilage
• food spoilage
– results from growth of microbes in food
• alters food visibly and in other ways, rendering it
unsuitable for consumption
– involves predictable succession of microbes
– different foods undergo different types of spoilage
processes
– toxins are sometimes produced
• algal toxins may contaminate shellfish and finfish
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50. Food Spoilage
•Approximately 1/3rd of all food manufactured in
world is lost to spoilage
•Microbial content of foods (microbial load):
qualitative (which bugs) and quantitative (how many
bugs)
•Shelf life
•Non-perishable foods (pasta)
•Semiperishable foods (bread)
•Perishable foods (eggs)
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51. Minimize contamination by:
1. Good management processes
2. Acceptable sanitary practices
3. Rapid movement of food through processing
plant
4. Well-tested preservation procedures
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52. Source Common Food Spoilage
•Meat
•Cutting board contamination
•Conveyor belts
•Temperature
•Failure to distribute quickly
•Fecal bacteria from intestines
•Fish
•Polluted waters
•Transportation boxes
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53. Cont……
•Poultry and Eggs
•Human contact
•Penetration by bacteria
•Milk and Dairy Products
•Lactobacillus and Streptococcus species that survive
pasturization (sour milk)
•Breads
•Spores and fungi that survive baking
•Grains
•Fungi produce toxins
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54. >>>>Food Microbiology
• Foodborne Illnesses
– Due to consumption of spoiled foods or foods
containg harmful microbes or their products
– Two categories of food poisoning
• Food infections
– Consumption of living microorganisms
• Food intoxications
– Consumption of microbial toxins rather than the microbe
– Symptoms include nausea, vomiting, diarrhea,
fever, fatigue, and muscle cramps
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55. Preventing Foodborne Disease
•Food infections (microbes are transferred to
consumer)
•Food poisoning (results from the toxin
consumption)
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56. WALTER WAKHUNGU WASWA
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57. FOOD POISONING
1. Food intoxication: Illness is caused by ingestion
of food with
• preformed toxin.
Examples of food intoxication
• Bacillus cereus 1-6 hours Vomiting, cramp Rice,
Pasta dishes
• Staphylococcus aureus 2-4 hours Vomiting Meat,
Salads
• Clostridium botulinum 12-72 hours Flaccid
paralysis Meat, Vegetables
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58. 2. Food infection: Illness is caused by ingestion
of food with microorganism.
• Incubation period and severity of disease in
food infection is determined by inoculum of
micro-organism ingested.
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59. LABORATORY DIAGNOSIS OF FOOD POISONING
• Specimen: Left over food, vomits, stool
• Culture the specimen for microbial isolation.
• Serological technique for toxin isolation.
• Treatment: Depends on the causative agent.
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60. MYCOTOXINS
• Ergotism
– toxic condition caused by growth of a fungus in
grains
• Aflatoxins
– carcinogens produced in fungus-infected grains
and nut products
• Fumonisins
– Carcinogens produced in fungus-infected corn
• ACRATOXINS
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61. WALTER WAKHUNGU WASWA
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62. Controlling Food Spoilage
1
2
3
4
5
6
7
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63. Canned food spoilage organisms may be
characterized as follows:
• Mesophilic organisms
-Putrefactive anaerobes
-Butyric anaerobes
-Aciduric flat sours
-Lactobacilli
-Yeasts
-Molds
• Thermophilic organisms
-Thermophilic anaerobes producing sulfide
-Flat-four spores
-Thermophilic anaerobes not producing
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64. WALTER WAKHUNGU WASWA
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65. Radiation
1.ultraviolet (UV) radiation
– used for surfaces of food-handling equipment
– does not penetrate foods
2.Gamma radiation
– use of ionizing radiation (gamma radiation) to
extend shelf life or sterilize meat, seafoods,
fruits, and vegetables
3.Beta rays-may be defined as a stream of
electrons emitted from radioactive
substances.
4.Microwaves
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66. NATURE RADIATION RESISTANCE
OF MICROORGANISMS
• The most sensitive bacteria to ionizing
radiation are gram-negative rods such as the
pseudomonas
• the coccobacillary-shaped gramnegative cells
of moraxellae and acinetobacters are among
the most resistant of gram negatives.
• Gram-positive cocci are the most resistant of
nonsporing bacteria, including
micrococci,staphylococci, and enterococci.
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67. IRRADIATION
• Types of Organisms
• Gram-positive bacteria are more resistant to
irradiation than gram negatives.
• Spore formers are more resistant than nonspore formers.
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68. Characteristics of radiation
resistant microorganisms
1).can survive 15 kGy eg D. radiophilus
2).contain red water-insoluble pigments
(carotenoid) plasma membrane is red,
3).contain L-ornithine as the basic amino
acid in their murein
4).Posses an outer membrane
5).High content of fatty acid in their envelope
6).Abudant DNA-Actively dividing cells may
contain 4 to 10 copies
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69. EFFECTIVENESS OF RADIATION
TECHNOLOGY IS DETERMINED BY:
1.Numbers of Organisms The larger the number
of cells, the less effective is a given dose.
2.Composition of Suspending Menstrum
(Food)
• Microorganisms in general are more sensitive
to radiation when suspended in buffer solutions
3.Presence or Absence of Oxygen
• The radiation resistance of microorganisms is
• greater in the absence of oxygen than in its
presence
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70. 4.Physical State of Food
• The radiation resistance of dried cells is, in
• general, considerably higher than that for
moist
• cells.
5.Age of Organisms
• Bacteria tend to be most resistant to
radiation
in the lag phase just prior to active cell division.
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71. How do we effectively Detect FoodBorne Pathogens?
First the method must be rapid and sensitive
• methods include:
– culture techniques – may be too slow
– immunological techniques - very sensitive
– molecular techniques
• probes used to detect specific DNA or RNA
• sensitive and specific
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72. Surveillance for food-borne
disease
• PulseNet
– established by Centers for Disease Control
– uses pulsed-field gel electrophoresis under
carefully controlled and duplicated conditions to
determine distinctive DNA pattern of each
bacterial pathogen
– enables public health officials to link pathogens
associated with disease outbreaks in different
parts of the world to a specific food source
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73. Surveillance…
• FoodNet
– active surveillance network used to follow nine
major food-borne diseases
– enables public health officials to rapidly trace the
course and cause of infection in days rather than
weeks
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74. Helpful Suggestions
•Refrigerate quickly
•Wash hands
•Clean cutting boards
•Leftovers
•Avoid home-canned foods
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75. Microbiology of Fermented
Foods
• Major fermentations used are lactic,
propionic, and ethanolic fermentations
• Fermentation=Any partial breakdown of
carbohydrates taking place in the absence
of oxygen.
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76. WALTER WAKHUNGU WASWA
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77. WALTER WAKHUNGU WASWA
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78. Meat and Fish Fermented Products
•
•
•
•
•
•
Sausages
Hams
Bologna
Salami
Izushi – Fish, Rice And Vegetables
Katsuobushi – Tuna
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79. Wine
White vs. Red: juice or juice and skin
Yeasts: Ferment when no oxygen around.
Saccharomyces species
Dry
Sweet
Sparkling
Fortified
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80. Production of Breads
• involves growth of Saccharomyces cerevisiae (baker’s
yeast) under aerobic conditions
– maximizes CO2 production, which leavens bread
• other microbes used to make special breads (e.g.,
sourdough bread)
• can be spoiled by Bacillus species that produce
ropiness
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81. Other Fermented Foods
• silages
– fermented grass, corn, and other fresh animal feeds
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82. Microorganisms as Foods and Food
Amendments
• variety of bacteria, yeasts, and other fungi are
used as animal and human food sources
• probiotics
– microbial dietary adjuvants
– microbes added to diet in order to provide health
benefits beyond basic nutritive value
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83. PSYCHROPHILICMICROORGANISMS
• This term is applied to organisms that grow
over the range of subzero to 20C.Are those
organisms capable of growing relatively
rapidly at commercial refrigeration
temperatures with out reference to
optimum temperature for growth. Species
of Pseudomans, Achromobacter,
flavobacterium and Alcahigenes are
examples of Psychrophilic bacteria.
• Large no=change in flavors as well as defects
in foods.
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84. Thermophilic microorganism
 Thermophilic microorganisms are those
organisms which will survive so significant
measure of heat treatment . The thermophilic
organisms not only survive the heat treatment
but also grow at the elevated temperature
. Thermoduric bacteria are important with
regard to milk and milk products as they may
survive pastourisation temperature.
Those of greatest importance in foods belong to
the genera Bacillus, Clostridium, and
Thermoanaerobacterium.
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85. XTERISTICS OF THERMOPHYLIC
MICROORGANISMS
• On the basis of growth temperatures,
thermophiles may be characterized as
organisms with a minimum of around 45C, an
optimum between 50C and 60C, and a
maximum of 70C or above.
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86. EXAMPLES
• Genera Lactobacillus, Bacillus and Clostridium
are recognized as containing some species
which will qualify as thermoduric.
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87. STAPHYLOCOCCUS
•
•
•
•
The three main species of clinical importance
Staphylococcus aureus
Staphylococcus epidermidis
Staphylococcus saprophyticus
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88. cont
• Can readily grow in ordinary media under
aerobic and microaerophilicconditions
• grow most rapidly at 37 0c but form pigment
best at room
• temperature of 20-25 oc
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89. cont
• Some of them are normal flora of the skin and
mucus membrane of human, otrhhers cause
suppuration abscess
• Formation and fatal septicemia
• Produce catalase, which differentiate them
from the streptococci.
• Converts H202 into H20 and 02
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90. toxins
 Exotoxins(α, β, γ, δ)
 . Enterotoxin-Produced by S.aureus when
grown in
 carbohydrate and protein foods.
 Multiple (A-E, G-I, K-M) soluble heat-stable,
gut enzyme resistant toxins which act on
neural receptors in the gut to stimulate
vomiting center in the central nervous
system.
 It is superantigen causing staphylococcal
food poisoning
 .
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91. cont
• Toxic shock syndrome toxin- Superantigen
desquamative toxin Produced by S.aureus and
Causes fever, shock,multiple-organ failure and
skin rash.
• . Exfoliative toxin-Epidermolytic superantigen
produced by
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92. Incidence in Delicatessen and
related foods
• Delicatessen foods, such as salads and
sandwiches, are sometimes involved in foodpoisoning outbreaks. These foods are often
prepared by hand, and this direct contact may
lead to an increased incidence of food poisoning
agents such as Staphylococcus. Once organisms
such as these enter meat salads or sandwiches,
they may grow well because of the reduction in
numbers of the normal food biota by the prior
cooking of salad ingredients.
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93. incidences
• Most microorgansm are enteric bacteria and
some environmental fungi
• Staphylococcus
• S.aureus
• C.perfringens
• E.coli
• Yeast and moulds
• Corliforms
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94. Determining microorganisms and
their products in food
• The examination of foods for the presence,
types, and numbers of microorganisms and/or
their products is basic to food microbiology.
• Culture
• Microscopic examination
• Sampling
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95. Direct microscopy
In its simplest form, the DMC consists of
making smears of food specimens or cultures
onto a microscope slide, staining with an appropriate
dye, and viewing and counting cells with
the aid of a microscope (oil immersion objective).
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96. sterilization
: Destruction of all forms of microbial life including
spores.
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97. How would you determine
efficiency of a sterilizer
1. Recording of temperature and time of each
sterilizing cycle.
2. Heat-sensitive autoclave tape fixed to the outside
of each pack.
.. Color change of autoclave tape from blue to
brown-black indicates completesterilization.
4. Biological indicator : Use of paper strips
impregnated with spores of Bacillus
stereothermophilus
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98. Quality of water
 quality of water is odorless, colorless, tasteless and free from
fecal pollution and harmful chemicals.
Human illness is caused by water supplies becoming
contaminated from feces being passed or washed into rivers,
streams, or being allowed to seep into wells.
Feces contain microorganisms like Escherichia coli,
Streptococcus
faecalis and Clostridium perfringenes, which contaminate safe
water.
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99. lab
Determining whether a water supply is fecally polluted is to
test for the presence of normal fecal organism.
Testing for normal fecal organisms as indicators of fecal
pollution is a reliable way of determining whether water is
bacteriologically safe to drink.
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100. coliforms
Organisms used as indicators of
fecal pollution are the coliform
group particularly E. coli.
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101. Food contamination
Food may acquire their micro-organism from various sources
and the following are the important sources.
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102. 1. Animals
- Animals could be a source of contamination
of food.
- The surface of animals, the respiratory
tract, the gastrointestinal tract, hides,
Loofs and waste products of animals are
important sources of contamination.
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103. 2. Plants
- Food may get their microbial contamination from green
plants.
- The natural flora of growing plants includes pseudomonas,
alcaligenes,bacissus, Micrococcus, coliform etc.
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104. 3. Sewage
- Gastrointestinal pathogens, coliforms,
Enterococci of untreated domestic
sewage could be source of contamination
of raw plant foods.
- Sewage can also contaminate natural
waters and contribute micro-organisms to
shellfish, fish and other sea foods.
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105. 4. Soil
- Soil is a very rich environment in microbes
and is a major source of contamination of
food.
- Bacillus, clostridium, enterobacter,
Escherichia, Micrococcus, Alkaligens,
Flavobacterium, Pseudomonas, proteus,
Aerobacter, molds and yeast are kinds of
organisms that contaminate food from
soil.
5. Air and water:- are also important source of
food
contamination.-
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106. MICROORGANISM IMPORTANT IN FOOD
1.Indicator microoganisms
Indicator organisms are bacterial groups
(or
species) whose presence in foods, above a
certain
numerical limits, is considered to indicate
exposure
of food to conditions that might introduce
hazardous
organisms and/or allow proliferation of
pathogenic or
toxinogenic species.
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107. Indicator organisms
Include coliforms and faecal
streptococci.
Coliform group is defined to include all aerobic
and
faculitative anaerobic, gram negative, non-spor
forming, rod shaped species which ferment
lactose
with the production of acid and gas within 48
hours
at 35C
• Coliform are either part of the normal flora of
intestinal tract of man and animals or found in
environments such as soil and plants.
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108. Coliform that are commonly found in the intestinal
tracts of man and animals (faeces) are called faecal
coliform and those coliforms that are normal
inhabitants of soil and plants are called non faecal
coliform.
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109. 2.INDEX MICROORGANISMS
=is one whose presence implies the
possible occurance of a similar but pathogenic
organism.E. coliis used an index organism and
its presence indicates possible presence of
pathogenic enteriobacteriacea eg.salmonellae
species.
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110. 3.FOOD POISONING MICROORGANISMS
• those which cause the disease by
infection
• those which produce toxin in food
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111. Those which cause infection must grow in
food in large numbers and cause infection
when consumed together with food. The
most most common microorganisms
includes salmonella tyhimurrium,
entropathogenicE.coli,Vibrio
parahaemolyticus etc.
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112. Those which cause intoxication must grow
in food large numbers and produce
enough toxin and when consumed
together with food cause intoxication.The
most common microorganism in this
group are clostridium
botulinium,staphylococcus and toxigenic
fungi eg. Aspergillus flavus.
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113. 5.INFECTIOUS MICROORGANISMS
Organisms whose presence in small numbers in
food and when consumed can cause infection.
In this case the food acts as avector but not
necessarly as a growth medium.organisms in
this group are, Vibrio choleraeO1, salmonella
typhi, shigella sonnei,Bacillus anthracis,
HepatitisB virus etc.
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114. 6.Spoilage microorganisms
The spoilage microorganisms include bacteria, yeasts
and
moulds that cause undesirable changes of the
appearance,
odour, texture or taste of the food. They are commonly
grouped
according to their type of activity or according to theiri
growth
reguirements.
a) Psychrophilic microorganisms
b) Lipolytic Microorganisms
c) Proteolytic microorganisms
d) Halophilic microorganisms
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114

115. f)Acid producing
microorganisms
g)Yeasts and moulds
h)Mesophillic spore forming
aerobes
i)Thermophillic anaerobes
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116. Microbiological examination of
food
• Sampling should be carried
• Sampling
out aseptically
• It is important to not
• Samples should be
that samples of foods
protected against
collected for
extraneous contamination
microbiological analysis
• Moreover, samples must
should reflect the
be held under conditions
microbiological
thatpermit neither die off
condition at the time of
nor multiplication of the
collection. This implies
original
that
• microflora present in the
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food.

117. Terms used
• A LOT:Is a quantity of
food produced and
handled under uniform
• condition. This means
that food produced
within a batch or
• in a continuous process
a food produced within
a limited
• period of time
• FILED SAMPLE:The
amount of material
actually used in the
analysis of food for
microorganisms. The
sample unit is
recommended to be 25
g for
all types of food
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118. Microbiological criteria
• is a microbiological
value (eg. Number of
microorganism per g of
food) or a range
established by use of
defined procedures and
includes the following
information.
• ENDELEA
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119. STAPHYLOCOCCUS
• Characteristics:
• Gram positive non spore-forming non-motile,
spherical cells, usually arranged in grape-like
clusters
• The three main species of clinical importance
• Staphylococcus aureus
• Staphylococcus epidermidis
• Staphylococcus saprophyticus
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120. HABITAT
• Some of them are normal flora of the skin and
mucus membrane of human, others cause
suppuration abscess formation and fatal
septicemia
• relatively resistant to drying , heat, and 9%
NacI, but readily inhibited by 3 %
hexachlorophene
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121. TOXINS PRODUCED BY STAPHYLOCOCCUS
. Exotoxins(α, β, γ, δ)
. Enterotoxin-Produced by S.aureus when grown in
carbohydrate and protein foods.
Multiple (A-E, G-I, K-M) soluble heat-stable, gut enzyme
resistant toxins which act on neural receptors
in the gut to stimulate vomiting center in the central nervous
system. It is superantigen causing staphylococcal food
poisoning
. Toxic shock syndrome toxin- Superantigen desquamative
toxin Produced by S.aureus and Causes fever, shock,
multiple-organ failure and skin rash.
. Exfoliative toxin-Epidermolytic superantigen produced by
S.aureus and uses generalized desquamation of the skin.
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122. . Food poisoning: Caused by
enterotoxin produced by S.aureus
PREVENTION AND CONTROL?
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123. STREPTOCOCCUS
• They are non-motile, non- sporulating, grampositive facultative anaerobes
• Spherical or oval cells characteristically
forming pairs or chains during growth.
• They are widely distributed in nature and are
found.
• in upper respiratory tract, gastrointestinal
tract and genitourinary tract as normal
microbial flora.
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124. BACILLUS
• Characteristics:
• • Aerobic, non-motile,spore-forming, grampositive chain
• forming rods.
• • Bacillus species are ubiquitous saprophytes
• Important human pathogen
• B. anthracis
• B. cereus
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125. B.CEREUS
• General characteristics:
• Exhibit motility by swarming in semisolid
media
• Produce β lactamase, so not sensitive to
penicillin
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126. CLINICAL FEATURES
• 1. Food poisoning
Pathogenicity determinant: Exotoxin
a.Emetic type food poisoning IP is 1-5 hrs after
ingestion of preformed toxin contaminating rice
and pasta dishes Characterized by nausea,
vomiting, abdominal cramps, and self-limited with
in 24 hrs
b. Diarrheal type food poisoning IP is 1-24 hrs after
ingestion of contaminated meat dishes with
sporulating or preformed toxin Characterized by
profuse diarrheaand abdominal cramps. Fever
and vomiting is uncommon
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127. CONTROL AND PREVENTION
• YOU KNOW?
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128. CLOSTRIDIUM PERFRINGEN
• Characteristics:
• Clostridia are anaerobic, spore-forming motile,
gram-positive rods.
• Most species are soil saprophytes but a few
are pathogens to human.
• They inhabit human and animal intestine, soil,
water, decaying animal and plant matter
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129. PATHOGENICITY
• 1. Enzymes: Digest collagen of subcutaneous
tissue andmuscle.. Collagenase. Proteinase.
Hyaluronidase. Dnase
• 2. Toxins. PhospholipaseC (α toxin)
• It has lethal, necrotizing and hemolytic effect
on tissue. It causes cell lysis due to lecithinase
action on the lecithin which is found in
mammalian cell membrane.
• . Theta toxin It has hemolytic and necrotic
effect on tissue.
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130. Clinical manifestation:
• 1. Clostridial myonecrosis: Gas gangrene
• . IP(Incubation period) =1-3 days
Colonization of devitalized tramatized wound by
C.perfringens spores, and organism germiation
and release of toxins
Presentation: Muscle and subcutaneous tissue
necrosiss andcrepitationFoul smelling wound
discharge
• Fever, toxaemia, hemolytic anemia, Shock
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131. CLOSTRIDIUM BOTULINUM
• • Spores of C. botulinum are widely
distributed in soil, they often contaminate
vegetables, fruits and other materials.
• Produce a neurotoxin which is the most active
• known poison, and considered to be the
major agent of bioterrorism and biologic
warfare
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132. PATHOGENESIS
• 1. Food botulism
. INCUBATION PERIOD = 18-24 hrs
. Route of entry is under cooked consumption of
C.botulinum toxin contaminated spiced, smoked,
vaccumpacked or canned food
.The toxin is absorbed from the gut and acts by
blocking the release of acetylcholine at synapses
and neuromuscular junction and manifests with
flaccid paralysis and visual disturbance, inability
to swallow, and speech difficulty.Death is
secondary to respiratory failure or cardiac arrest
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133. CONT…
• 2. Infantile botulism C.botulinum implicated
and affects infants when mixed feeding starts
(after fourth month of life).
• Ingestion and colonisation of the gut with
C.botulinum, and production of toxin and
adsorption of toxin leads to poor feeding,
paralysis (floppy baby), and cranial nerve
palsy.
• Diagnosed by demonstration of the organism
or toxin from the stool.
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134. BRUCELLOSIS
• Brucellosis/ Undulant fever
• 2 stages of illness
1. Acute stage: Fever, malaise, sweating,
hepatosplenomegally, lymphadenopathy
• Associated with 80% spontaneous recovery
• Prevention and control:
Pasteurization of milk and milk products
Slaughter of all infected animals in dairy herds
Vaccination of cattle.
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135. ESCHERICHIA COLI
• Characteristics:
• . Normal flora in human and animal
gastrointestinal tract.
• . Found in soil, water and vegetation.
• . Most are motile; some are capsulated.
• . E.coli-associated diarrheal disease
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136. DIARRHOEA
• 1. Enteropathogenic E.coli(EPEC) . causes
outbreaks ofself-limiting infantile diarrhea
. they also cause severe diarrhea in adults
• 2. Enteroinvasive E.coli(EIEC) invade
the mucosa of the ileum and colon, and causes
shigellosis-like dysentery
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137. 3. Enterotoxigenic E.coli(ETEC) adherence to
epithelial cells of small intestine followed by release
of enterotoxin which causes toxin-mediated watery
diarrhea in infants and young adults.
. It is an important cause of traveller’s diarrhea
4. Entero haemorrhagic E.coli( EHEC) causes
haemorrhagic colitis (severe form of diarrhea)
5. Enteroaggressive E.coli( EAEC) .Adhere to human
intestinal mucosal cells and produce ST-like toxin and
hemolysin, and causes acute and chronic diarrhea
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138. SALMONELLA
• Species of medical importance are:S. typhi S.
paratyphi S. enteritidis
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139. CLINICAL PATHOGENESIS
• 1. Enteric fever:It is caused by S.typhi and
S.paratyphi, and transmitted by fecal-oral
route via contaminated food and drinks
Incubation period: 10-14 days
Predisposing factors:
.Reduced gastric acidity
.Disrupted intestinal microbial flora
.Compromised local intestinal immmunity
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140. CONT..
• Both manifest with persistent fever,
headache,
malaise, chills, enlargement of liver and spleen,
and skin rashes.
• Paratyphoid fever is milder than typhoid fever
Complications:
Intestinal perforation
Lower gastrointestinal bleeding
Dissenmination to different body organs
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141. 2. Gastroenteritis
•
•
•
•
•
•
•
•
It is caused by S. enteritidis
S. typhimurium
IP= 8-48 hrs
It manifests with initial watery diarrhea, and
later
bloody mucoid diarrhea associated with
crampy
abdominal pain and tenesmus.
Bacteremia is rare (2-3 % of cases)
It usually resolves in 2-3 days
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142. SHIGELLOSIS
•
•
•
•
•
S. dysenteriae
S. flexneri
S. boydii
S. sonnei
In developing countries, shigellosis (bacillary
dysentery) is caused by S. flexneri and S.
dysenteriae.
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143. • Pathogenesis and Clinical features:
• Route of infection is fecal-oral route Inoculum
dose: 103 organisms
Pathogenicity determinant:Toxins:
• Endotoxin: irritate the bowel wall
• Exotoxin: Enterotoxin and neurotoxin
• S.dysenritiae type 1(shiga bacillus) produce
heat labile exotoxinmediated diarrhea
• IP: 1-2 days
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144. • It causes shigellosis (bacillary dysentery)
characterized by sudden
• onset of bloody mucoid diarrhea, abdominal
cramp, tenesmus, fever,
• generalized muscle ache and weakness.
• Complication: Dehydration
• Electrolyte and acid-base disturbance
• High prevalence: Poor sanitation
• Poor personal hygiene
• Polluted water supply
• Young children are frequently affected.
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145. YERSINIA
• Animals are natural hosts of yersinia, and
humans are accidental hosts of yersinia
infection
• Important human pathogens
• Y. pestis
• Y. pseudotuberculosis
• Y. enterocolitica
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146. • Yersinia pestis
• . Plague bacillus with gram negative, nonmotile, facutatively
• anaerobe possessing bipolar granules
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147. • Pathogenesis and clinical features:
• Rat flea (Xenopsylla cheopis) gets infected by
biting an infected rodent → infected rat flea
bites human (accidental host) → organism
migrate to regional lymphnodes from the
site of bite (bubonic plaque) and gets into the
blood via lymphatics (septicemic plaque), or
Primary pneumonic plaque results from
inhalation of infective droplets, usually from
an infected coughing person
• IP=2-6 days
• Human Plaque: 3 types
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148. •
•
•
•
•
•
•
1. Bubonic plague: Fever, vomiting, painful
lymphadenitis(buboes) in the groin or axillae
2. Pneumonic plague: Ip is 1-3 days
Profuse mucoid or bloody expectoration with
signs of pneumonia
3. Septicemic plague
Fever, vomiting, diarrhea, hypotension,
altered
• mentation, renal and heart failure, intra
vascular
• coagulopathy
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149. • HUMAN INFECTION
• Human infection results from ingestion of
food and drinks contaminated by animal feces
• Antigenic structure
• . Inv (invasion) locus
• . AIL (attachement invasion locus)
• Pathogenesis and clinical feature:
• Route of transmission: Contaminated food
and drinks
• Inoculum dose: 108-109 org
• IP=5-10 days
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150. Cont…
• . Fever, abdominal pain, toxin and invasionmediated diarrhea
• Usually self-limited disease
• Post-diarrheal diseases
• Arthritis
• skin rash/nodules
• Complication: Sepsis/ Meningiti
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151. VIBRIO
. Actively motile, gram-negative curved rods.
. Species of medical importance: Vibrio cholerae
• Characteristics:
1.Found in fresh water, shellfish and other sea
food..Man is the major reservoir of V.
cholerae-01, which causes epidemic cholera.
2. Readily killed by heat and drying; dies in
polluted water but may survive in clean
stagnant water, esp. if alkaline, or sea water
for 1-2 weeks.
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152. • CLINICAL FEATURES:
• Route of infection is fecal-oral route.
• After ingestion of the V.cholerae-01, the
bacteria adheres to the intestinal wall with
out invasion then produces an exotoxin
causingexcessive fluid secretion and
diminished fluid absorption resulting in
diarrhea (rice water stool) which is
characterized by passage of voluminous
watery diarrhea containing vibrios, epithelial
cells and mucus; and result in severe
dehydration.
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153. CAMPYLOBACTER
• Characteristics:
• Small, delicate, spirally curved gram-negative
bacteria.
• Motile bacteria with single polar flagellum.
• . Stricly microaerophilic bactria requiring 510% o2 and 10% co2 enriched environment.
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154. Clinical features:
• Inoculum dose: 104 organisms
• Source of infection is contaminated food,
drinks,and unpasteurized milk
• The organism multiply in small intestine, invade
the epithellium and produce inflammation
Campylobacter enteritis manifests with fever,
headache, malaise, crampy abdominal pain and
bloody mucoid diarrhea, and usually selflimited enteritis in a week period
• Laboratory diagnosis:
• Specimen: Stool
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155. LISTERIOSIS
• General characteristics:
• . Widely present in plants, soil and surface
water
• . Zoonotic pathogen of domestic animals
• . Non-sporulating, facultative anaerobe,
intracellular. Gram positive rods
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156. Pathogenesis and clinical features:
• Transmitted to humans through ingestion of
poorly coooked
• meat and unpasteurized milk and milk
products
• 1. Perinatal human listeriosis: Granulomatous
• infantisepticum
• . Early onset syndrome: Intrauterine sepsis
• . Late onset syndrome: Neonatal meningitis
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157. Cont……
• In Adults
• . Meningoencephalitis
• . Bacteremia
Prevention and control:
• Proper cooking of animal souce foods
• Pasteurization of milk and milk products/
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158. parasites
• The animal parasites that can be contracted
by eating certain foods belong to three distinct
groups: protozoa, flatworms, and roundworms.
• Animal parasites do not proliferate in foods.
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159. PROTOZOA
• Giardiasis Giardia lamblia is a flagellate
protozoan that exists in environmental
waters.
• The protozoal cells (trophozoites) produce
cysts, which are the primary forms in water
and foods.
• Upon ingestion, Giardia cysts excyst in the
• gastrointestinal tract with the aid of stomach
acidity and proteases and give rise to clinical
giardiasis in some individuals.
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160. • Excystation of the trophozoites occurs
somewhere in the upper small intestine, and
this step is regarded as being equivalent to a
virulence factor.
• The trophozoites are not actively phagocytic,
and they obtain their nutrients by absorption.
Occasionally, bile ducts are invaded, leading
to cholecystitis.
• ENVIRONMENTAL DISTRIBUTION
• Water=waterborne
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161. giardiasis
• The incubation period for clinical giardiasis
is 7-13 days, and cysts appear in stools after
3-4 weeks. Asymptomatic cyst passage is the
most benign manifestation of G. lamblia
infectionin humans, but when clinical giardiasis
occurs, symptoms may last from several months
to a year or more. Up to 9.0 x 108 cysts are shed
each day by patients, and they may survive as
long as 3 months in sewage sludge.
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162. Clinical symptoms
•
•
•
•
•
•
•
Abdominal cramps
Abdominal distention
Weigh loss
Diarrhoea
Fatigue
Vomiting
Nausea
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163. • Giardiasis is a highly contagious disease. It
has been documented in daycare centers where
unsanitary conditions prevailed. The human
infection rate ranges from 2.4% to 67.5%.18
The minimum infectious dose of G. lamblia
cysts for humans is 10 or less.
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164. Giardiasis is diagnosed by the demonstration
• of trophozoites in stool specimen by
microscopic examinations using either wet
mounts or stained specimens. G. lamblia can
be grown in axenic culture, but this does not
lend itself to rapid diagnosis.
• Effective enzyme-linked immunosorbent
assay (ELISA) tests have been developed.
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165. The drug of choice for the
treatment of giardiasis
• is quinacrine, an acridine derivative. Also
effective are metronidazole and tinidazole.
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166. Incidence in Foods and Foodborne
Cases
• Giardia has been shown to occur in some
vegetables, and it may be presumed that the
organism occurs on foods that are washed
with contaminated water or contaminated by
unsanitary asymptomatic carriers.
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167. Amebiasis
• Amebiasis (amoebic dysentery), caused by
Entamoeba histolytica, is often transmitted by
the fecal-oral route, although transmission is
known to occur by water, food handlers, and
Foods.
• In warm stools from a case of active
dysentery, E. histolytica is actively motile and
usually contains red blood cells that the
protozoan ingests by pseudopodia.
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168. • Although generally outnumbered in stools by
Entamoeba coli, the latter never ingests red
blood cells.
• Although the trophozoites do not persist
under environmental conditions, the
encysted forms can survive as long as 3
months in sewage sludge.
• The possible transmission of cysts to foods
becomes a real possibility when poor personal
restroom hygiene is practiced.
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169. •
•
•
•
•
In its trophozoite stage, the organism induces
infection in the form of abscesses in intestinal
mucosal cells and ulcers in the colon.
It reproduces by binary
fission in the large intestine. It encysts in the
ileum,
• and cysts may occur free in the lumen. The
• organism produces an enterotoxic
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170. • Syndrome, Diagnosis, and Treatment
The incubation period for amebiasis is 2-4
weeks, and symptoms may persist for several
• months. Its onset is often insidious, with loose
• stools and generally no fever. Mucus and
blood
• are characteristic of stools from patients.
Later
• symptoms consist of pronounced abdominal
• pain, fever, severe diarrhea, vomiting, and
lumbago,
• and somewhat resemble those of shigellosis.
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171. • Amebiasis is diagnosed by demonstrating
trophozoites
• and cysts in stools or mucosal
• scrapings. Immunological methods such as
indirect
• hemagglutination, indirect
immunofluorescence,
• latex agglutination, and ELISA are
• useful.
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172. • This syndrome can be treated with the
amebicidal drugs metronidazole and
chloroquine.
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173. • Toxoplasmosis
• This disease is caused by Toxoplasma gondii,
• a coccidian protozoan that is an obligate
intracellular
• parasite.
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174. • Domestic and wild cats are the only definitive
hosts for the intestinal or sexual phase of this
organism, making them the primary sources
of human toxoplasmosis. Normally, the
disease is transmitted from cat to cat, but
virtually all vertebrate animals are susceptible
to the oocysts shed by cats. As few as 100
oocysts can produce clinical toxoplasmosis in
humans, and the oocysts can survive over a
year in warm, moist environments.
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175. • Symptoms, Diagnosis, and Treatment
• In most individuals, toxoplasmosis is
symptomless,but when symptoms occur, they
consist of fever with rash, headache, muscle
aches and
• pain, and swelling of the lymph nodes. The
• muscle pain, which is rather severe, may last
up
• to a month or more.
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176. cycle
• The disease is initiated upon the ingestion of
• oocysts (if from cat feces), which pass to the
intestine
• where digestive enzymes effect the release
• of the eight motile sporozoites.
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177. • Fresh meats may contain toxoplasma oocysts.
• Undercooked meat was suspected to be the
source of human toxoplasmosis.
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178. • Control
• Toxoplasmosis in humans can be prevented by
avoiding environmental contamination with
cat feces and by avoiding the consumption of
meat and meat products that contain viable
tissue cysts. The cysts of 7. gondii can be
destroyed by heating meats above 600C or by
irradiating at a level of 30 krad (0.3 kGy) or
higher. The organism may be destroyed by
freezing.
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179. • Sarcocystosis
• Of the more than 13 known species of the
genus Sarcocystis, two are known to cause an
extraintestinal disease in humans. One of these
is obtained from cattle (S. hominis) and the
other from pigs (S. suihominis). Humans are
the definitive hosts for both species; the
intermediate host for S. hominis is bovines,
and pigs for S. suihominis.When humans
ingest a sarcocyst, bradyzoites are released
and penetrate the lamina propria of the small
intestine, where sexual reproduction occurs
that leads to sporocysts.
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180. • Since most of the above cases have been
traced to meats, the consumption of raw or
undercooked meats carries the risk of this
infection.
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181. Cryptosporidiosis
• The protozoan Cryptosporidiunparvum was
first described in asymptomatic mice, and for
decades now it has been known to be a
pathogen of at least 40 mammals and varying
numbers of reptiles and birds. Although the
first documented human case was not
recorded until 1976, this disease has a
worldwide prevalence of 1-4% among patients
with diarrhea,96 and it appears to be
increasing.
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182. • The prevalence of C. parvum in diarrheal
stools is similar to that of Giardia lamblia. In
humans, the disease is self-limiting in
immunocompetent individuals, but it is a
serious infection in the immunocompromised,
such as AIDS patients. The protozoan is known
to be present in at least some bodies of water
and thus exists the potential for food
transmission.The fecal-oral route of
transmission is the most important, but
indirect transmission by food and milk is
known to occur.
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183. • C. parvum carries out its life cycle in one
host. Following ingestion of the thick-walled
oocysts, they excyst in the small intestine and
free sporozoites that penetrate the microvillous
region of host enterocytes, where sexual
reproduction leads to the development of
zygotes.
They invade host cells by disrupting their own
membrane as well as that of the host.
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184. • Symptoms, Diagnosis, and Treatment
• The clinical course of cryptosporidiosis in
• humans depends on the immune state, with
the
• most severe cases occurring in the
immunocompromised.
• In immunocompetent individuals,
• the organism primarily parasitizes the
intestinal epithelium and causes diarrhea.
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185. • FLATWORMS
• AU flatworms belong to the animal phylum
• Platyhelminthes,
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186. • Fascioliasis
• This syndrome (also known as parasitic biliary
• cirrhosis and liver rot) is caused by the
digenetic
• txQmdXo&t Fasciola hepatica. The disease
• among humans is cosmopolitan in
distribution,
• and the organism exists where sheep and
cattle
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187. • in humans results
• from eating raw Fflsczo/fl-ladedbovine liver
• where young flukes become attached to the
buccal
• or pharyngeal membranes, resulting in pain,
• hoarseness, and coughing.18
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188. • Symptoms, Diagnosis, and Treatment
• Symptoms develop in humans about 30 days
• after the infection; they consist of fever,
general
• malaise, fatigue, loss of appetite and weight,
and
• pain in the liver region of the body.
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189. • Fasciolopsiasis
• Fasciolopsiasis is caused by Fasciolopsis buski,
and the habitat of this organism is similar to
that of E hepatica.
• Humans serve as definitive host,
• Snails serve as first intermediate hosts, and
water plants (watercress nuts) as second
intermediate hosts.
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190. • no symptoms
• occurring when only a few parasites exist In
the body. When symptoms occur, they
develop within 1-2 months after the initial
infection and consist of violent diarrhea,
abdominal pain, loss of weight, and
generalized weakness.
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191. • Paragonimiasis
• This parasitic disease (also known as parasitic
• hemoptysis) is caused by Paragonimus spp.,
especially P. westermani.
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192. Diphyllobothriasis
• Contracted from the consumption of raw or
undercooked fish,
• Causative organism, Diphyllobothrium latum,
fish tapeworm.
• Definitive hosts are humans andother fisheating mammals;
• Intermediate hosts are various freshwater fish
and salmon, where plerocercoid (or
metacestode) larvae are formed.
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193. • Symptoms, Diagnosis, and Treatment
• Although most cases of diphyllobothriasis are
• asymptomatic, victims may complain of
epigastric
• pain, abdominal cramps, vomiting, loss of
• appetite, dizziness, and weight loss. Intestinal
• obstruction is not unknown.
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194. • Prevention
• Diphyllobothriasis can be prevented in
humans
• by avoiding the consumption of raw or
• undercooked fish.
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195. • Cysticercosis/Taeniasis
• This syndrome in humans is caused by two
• species offlatworms: Taeniasaginata (also
Taeniarhynchus
• saginatus; beef tape) and Taenia
• solium (pork tape).
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196. • The adult worm consists
• of a scolex (head) that is about 1 mm in size
• and lacks hooks but has four sucking discs.
Behind
• the scolex is the generative neck, which
• segments to form the strobila composed of
proglottids.
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197. • fully developed embryos, and may survive for
• months. When the eggs are ingested by
herbivores,
• such as cattle, the embryos are released,
• penetrate the intestinal wall, and are carried
to
• striated muscles where they are transformed
• into larval forms designated cysticerci.
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198. • Symptoms, Diagnosis, and Treatment
• Most cases of taeniasis are asymptomatic
regardless
• ofthe Taenia species involved, but symptoms
• differ when humans serve as intermediate
• host.
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199. • ROUNDWORMS
• The disease-causing roundworms of primary
• importance in foods belong to two orders
ofthe
• phylum Nematoda.
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200. •
•
•
•
•
•
Phylum Nematoda
Class Adenophorea (= Aphasmidia)
Order Trichinellida
Genus Trichinella
Class Secernentea (= Phasmidia)
Order Rhabditida
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201. • Trichinosis
• Trichinella spiralis is the etiological agent of
• trichinosis (trichinellosis), the roundworm
disease
• of greatest concern from the standpoint of
• food transmission.
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202. • the trichinae are transmitted from host
• to host; no free-living stages exist. In other
words,
• both larval and adult stages of T. spiralis are
• passed in the same host. It is contracted most
• often from raw or improperly cooked pork
• products.
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203. • Although they
• may remain in the intestines for about a
month,
• no symptoms are produced.
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204. • As the larvae burrow into muscles
several weeks later, severe pain, fever, and
other
symptoms occur, which sometimes lead to
death
from heart failure (see below).
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205. Symptoms and Treatment
One to 2 days after the ingestion of heavily
encysted meat, trichinae penetrate the
intestinal mucosa, producing nausea,
abdominal pain, diarrhea,and sometimes
vomiting.
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206. Diagnosis
• Because the trichinae exist as coiled larvae in
• ovoid capsular cysts in skeletal muscles,
biopsies
• are sometimes performed on the deltoid,
biceps,
• or gastrocnemius muscles.
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207. Prevention and Control
• Trichinosis can be controlled by avoiding the
• feeding of infected meat scraps or wild game
• meats to swine and by preventing the
consumption
• of infested tissues by other animals.
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